1. Field of the Invention
The invention relates to tooling used to make construction materials, and in particular an extrusion die to fabricate a plastic skin on materials used for concrete forms.
2. Description of the Prior Art
Concrete is a widespread and popular building material both in the developed and developing nations. One of the major material costs associated with concrete construction is the cost of the material used to build the form into which the concrete is poured. The traditional material used for concrete forms is lumber and plywood, the cost of which is steadily increasing everywhere, and is particularly acquired at a dear price in many developing nations.
In addition to the lumber and plywood, many other types of materials have been used for concrete forms, including metal sheeting and plastics, the cost of which is substantially higher than plywood and lumber, although such materials are typically more durable and may be reused more times. In most cases, lumber and plywood sheeting can be reused in different concrete forming projects, at the most, two to three times before the material becomes unusable for a variety of factors. While metal is very durable and can be reused many times, metal sheeting and bracing used to support the heavy weight of wet concrete is difficult to work with, and once deformed or bent, becomes practically unusable in any other project. While plastic sheeting and plastic structural components have durability and reusability, and can be easily worked in the field, most of these components lack the strength necessary for heavy concrete form work unless the thickness and, therefore, the cost of such materials is increased beyond the point of economic reason. In addition, many plastic materials are brittle or become brittle after relatively short exposures to the elements.
The extrusion of a plastic or polymer skin onto rectangularly cross sectioned, manufactured lumber in such a manner as to obtain close tolerances of the outer envelope and good adhesion and tight binding of the skin to the underlying lumber or substrate is nontrivial. The problem of obtaining a good lamination becomes particularly difficult when the size of the lumber increases to sizes larger than 2".times.4".
Therefore, what is needed is some type of apparatus and methodology whereby plastic or polymeric skin can be economically laminated on a variety of sizes of material, particularly larger materials such as 2".times.6'"s or larger, which material can be repeatedly employed in concrete form work at a low cost similar to plywood and lumber yet with a durability like plastics or metals.